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Emacs 26.1

In scratch buffer I has text

KRW-EOS
hel-how
hello-how-ar
h-privet
kak-del
123-567
aaa-bbb
AAA-BBB
AAAA-BBBB
AAA-BB
AA-BBB
A-A
AAAAAAAAAA BBBBBB
AAA BBB
ZZZ-YYY

M-x regexp-builder

Input next regexp:

\b[A-Z]{3}-\b[A-Z]{3}

But I get message: No matches

enter image description here

Why?

KRW-EOS - is match!!!

a_subscriber
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    { and } match themself and don't have special meaning unless you escape them i.e. \{ and \}, (elisp) Syntax of Regexps says "The special characters are ‘.’, ‘*’, ‘+’, ‘?’, ‘[’, ‘^’, ‘$’, and ‘\’;". – xuchunyang Jan 04 '19 at 12:44
  • @xuchunyang: Please consider posting your comment as an answer. – Drew Jan 04 '19 at 14:02
  • @xuchunyang \b[A-Z]{3}-\b[A-Z]{3} - not help. Same result. – a_subscriber Jan 04 '19 at 15:21
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    @Alexei re-builder supports three different syntaxes to represent one regexp: read, string and rx. Take \b for example, the read syntax is "\\b" (the same as the actual Emacs Lisp code and read stands for Emacs Lisp reader); the string syntax is "\b" (the same as C-M-s, the minibuffer will escape \ for you); the rx syntax is (rx word-boundary) (it is also actual Emacs Lisp code but using rx). – xuchunyang Jan 04 '19 at 16:09
  • @Alexei and the default syntax is read, see the variable reb-re-syntax, so you need to escape \ by yourself. If you use string syntax, then that pattern will work. You can change syntax by changing reb-re-syntax or C-c C-i (reb-change-syntax). – xuchunyang Jan 04 '19 at 16:13
  • If re-builder shows “No matches”, then your pattern is definitively not a match. Claiming otherwise in your question is nonsensical -- you should be asking what is wrong with your regexp, rather than insisting that it is correct. – phils Jan 04 '19 at 21:15
  • Please also refer to https://emacs.stackexchange.com/q/5568 which will also help you with the different syntax options. – phils Jan 04 '19 at 21:16

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